U.S. Attorney David B. Barlow in Salt Lake City said Friday that the mine operator, Pepper Pike, Ohio-based Genwal Resources Inc., an affiliate of Murray Energy Corp, has agreed to plead guilty to two counts of violating mandatory health and safety standards and pay a $500,000 fine.

Six miners died at Crandall Canyon in an August 2007 collapse so powerful that it initially registered as a 3.9-magnitude earthquake. Another cave-in 10 days later killed two rescuers and a federal inspector.

The operation was called off after drilling into the mountain found no sign of the men.